Tailoring in-situ TiC-reinforced laser 3D printed β Ti–Nb alloy with graphite additions for biomedical implants

β-type titanium alloys, renowned for their low elastic moduli, combined with titanium carbide (TiC) reinforcements, have emerged as promising candidates for load-bearing and wear-resistant bioimplant components. However, the fabrication of β-type titanium matrix composites (β-TMCs) remains challenging, particularly in achieving a refined microstructure with a controlled reinforcement distribution. This investigation introduces an innovative approach using laser-based powder bed fusion (PBF-LB/M) for the in-situ fabrication of TiC-reinforced β-TMCs. Powder mixtures composed of β Ti-42Nb alloy and graphite (particle size ∼3 μm) were processed with graphite additions of 0.5, 1.0, 1.5, and 2.0 vol.%, resulting in TiC fractions of approximately 2, 4, 6, and 8 vol.%, respectively, in the PBF-LB/M as-built samples. The formation of TiC nanoparticles within the β-Ti matrix was confirmed by microstructural characterization, including TEM/STEM with EDS and ASTAR analyses. While lower graphite levels led to the formation of rod-shaped TiC precipitates ranging from tens to hundreds of nanometers, higher graphite content produced nearly spherical TiC particles, consistent with a hypereutectic solidification pathway where TiC forms as a primary phase. The increasing TiC fraction enhanced hardness; specifically, the Ti-42Nb+2.0C composite (∼239 HV) demonstrated a 13% increase compared to the unreinforced Ti-42Nb alloy (∼211 HV). The elastic modulus also increased with TiC content, reaching ∼72 GPa compared to ∼58 GPa for the alloy. Notably, all elastic modulus values were significantly lower than that of the Ti-6Al-4V alloy (∼110 GPa). These findings establish an alternative additive manufacturing route for the in-situ fabrication of β-TMCs with a refined microstructure and enhanced mechanical properties, offering new possibilities for load-bearing implants.